#include<stdio.h>
#include<string.h>
#include<errno.h>
#include<unistd.h>
#include<event.h>

void listen_cb(int fd, short events, void* arg);
void socket_read_cb(int fd, short events, void *arg);

int tcp_server_init(int port, int listen_num);
 
int main(int argc, char** argv)
{
    int listener = tcp_server_init(9999, 10);
    if( listener == -1 )
    {
        perror(" tcp_server_init error ");
        return -1;
    }
 
    struct event_base* base = event_base_new();//使用库中定义的全局指针
 
    //添加监听客户端请求连接事件
    struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST,
                                        listen_cb, base);
    event_add(ev_listen, NULL);
 
 
    event_base_dispatch(base);
 
    return 0;
}
 
 
 
void listen_cb(int fd, short events, void* arg)
{
    evutil_socket_t sockfd; //实际类型为 int类型，知识进行了重命名
 
    struct sockaddr_in client;
    socklen_t len = sizeof(client);
 
    sockfd = ::accept(fd, (struct sockaddr*)&client, &len );
    evutil_make_socket_nonblocking(sockfd);//设置成非阻塞的形式
 
    printf("accept a client %d\n", sockfd);
 
    struct event_base* base = (event_base*)arg;
 
    //仅仅是为了动态创建一个event结构体
    struct event *ev = event_new(NULL, -1, 0, NULL, NULL);
    //将动态创建的结构体作为event的回调参数
    event_assign(ev, base, sockfd, EV_READ | EV_PERSIST,
                 socket_read_cb, (void*)ev);
 
    event_add(ev, NULL);
}
 
 
void socket_read_cb(int fd, short events, void *arg)
{
    char msg[4096];
    struct event *ev = (struct event*)arg;
    int len = read(fd, msg, sizeof(msg) - 1);//读取获取到的数据
    //读取到长度小于0时 判断操作
    if( len <= 0 )
    {
        printf("some error happen when read\n");
        event_free(ev);
        close(fd);
        return ;
    }
 
    msg[len] = '\0';
    printf("recv the client msg: %s", msg);
 
    char reply_msg[4096] = "I have recvieced the msg: ";
    strcat(reply_msg + strlen(reply_msg), msg);
 
    write(fd, reply_msg, strlen(reply_msg) );//写数据并发送给客户端
}
typedef struct sockaddr SA;
int tcp_server_init(int port, int listen_num)
{
    int errno_save;
    evutil_socket_t listener;
 
    listener = ::socket(AF_INET, SOCK_STREAM, 0);
    if( listener == -1 )
        return -1;
 
    //允许多次绑定同一个地址。要用在socket和bind之间
    evutil_make_listen_socket_reuseable(listener);
 
    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(port);
 
    if( ::bind(listener, (SA*)&sin, sizeof(sin)) < 0 )
        goto error;
 
    if( ::listen(listener, listen_num) < 0)
        goto error;
 
 
    //跨平台统一接口，将套接字设置为非阻塞状态
    evutil_make_socket_nonblocking(listener);
 
    return listener;
 
    error:
        errno_save = errno;
        evutil_closesocket(listener);
        errno = errno_save;
 
        return -1;
}